Tests
1st tests to order
direct antiglobulin test
Test
Performed to identify whether antibodies or complement are bound to the donor cells.[3]
Recipient's post-transfusion red cells are washed and incubated with antihuman globulin (Coombs reagent).
Observation of agglutination is considered a positive test.
Immunoglobulin or complement factors have bound to red-cell surface antigens in vivo.
When hemolysis is brisk and all of the transfused red cells are rapidly destroyed, the post-transfusion direct antiglobulin test may be negative.
Result
positive result indicates hemolytic transfusion reaction
visual inspection of post-transfusion blood sample
Test
Release of free hemoglobin as a result of red-cell destruction results in pink-to-red appearance of the supernatant.
Result
may reveal evidence of hemolysis
repeat ABO testing on post-transfusion blood sample
Test
Should be done on a sample of blood from both the patient and the transfused component.
Result
may reveal incompatibility
post-transfusion urinalysis
Test
Free hemoglobin indicates hemolysis in acute hemolytic transfusion reaction.[3]
Result
may demonstrate the presence of free hemoglobin
Tests to consider
serum IgA levels
Test
Reserved for cases of anaphylactic reaction to transfusion. IgA-deficient patients with anti-IgA antibodies may experience anaphylactoid reaction from IgA-positive transfusion.[27]
Result
may be low
anti-IgA antibody testing
Test
Reserved for cases of anaphylactic reaction to transfusion. IgA-deficient patients with anti-IgA antibodies may experience anaphylactoid reaction from IgA-positive transfusion.[27]
Result
may be positive
serum tryptase level
Test
A marker of systemic mast cell activation. In cases of suspected anaphylactic reaction to transfusion, serum tryptase levels should be measured to aid with postacute confirmation of a diagnosis of anaphylaxis.[5][32]
In the UK, the National Institute for Health and Care Excellence (NICE) recommends taking two acute mast cell tryptase levels: the first should be obtained as soon as possible after emergency treatment has started; the second should be taken ideally within 1-2 hours (but no later than 4 hours) from symptom-onset.[32] NICE advises that a third sample may be required when the patient is followed up in the specialist allergy service to establish their baseline mast cell tryptase level.[32]
Similarly, a 2023 anaphylaxis practice parameter update commissioned by the Joint Task Force on Practice Parameters (JTFPP) suggests that an acute serum tryptase level should be measured as soon as possible (ideally within 2 hours of the onset of symptoms) and that this should be followed by a second serum tryptase measurement at a later time to establish the patient’s baseline level.[5]
An acute tryptase level that is elevated above the upper limit of normal (e.g., >11.4 ng/mL in many laboratories) is supportive of a diagnosis of anaphylaxis, as is an acute level that shows significant elevation from the patient’s baseline tryptase level (even where the acute level is still within the normal range, i.e., an acute tryptase level in the normal range does not rule out anaphylaxis).[5]
A baseline tryptase level ≥8 ng/mL may suggest other diagnoses such as hereditary alpha-tryptasemia or mastocytosis.[5]
Result
acute level may be elevated or normal and may be raised from the patient’s baseline level
serum alloantibody screen
Test
Post-transfusion testing may reveal antibody responsible for delayed hemolytic reaction.[3]
Result
may be positive
serum LDH
Test
May be performed to help identify presence of hemolysis, particularly when direct antiglobulin test is negative.[3]
Result
may be elevated
serum bilirubin
Test
May be performed to help identify presence of hemolysis, particularly when direct antiglobulin test is negative.[3]
Result
may be elevated
gram stain and culture of component and post-transfusion recipient samples
Test
Should be performed when transfusion-associated sepsis is clinically suspected.[4]
Positive Gram stain or cultures suggest transfusion-associated sepsis from contaminated component.[4]
Associated with platelets (bacterial contamination in 1/1000 to 1/2000 units) more than other components.[4][33][34]
Result
may be positive
biopsy of skin, gut or liver
Test
Should be performed when transfusion-associated graft-versus-host disease is suspected.[9]
Skin involved with the maculopapular rash should be biopsied.
Pathologist should be directed to evaluate for graft-versus-host disease.
Result
may show evidence of graft-versus-host disease
HLA typing
Test
Performed when transfusion-associated graft-versus-host disease is suspected.[9]
Diagnosis established if circulating lymphocytes have different HLA phenotype from host tissue cells.
Result
circulating lymphocytes may have different HLA phenotype from host tissue cells
platelet antibody screen
Test
Most common antigen implicated in post-transfusion purpura is (HPA-1a), against which antibodies are made.
Result
may be positive
serum haptoglobin
Test
May be performed to help identify presence of hemolysis, particularly when direct antiglobulin test is negative.[3]
Result
may be low
serum potassium
Test
Hypokalemia may be associated with large-volume blood transfusions due to citrate conversion to bicarbonate, which drives potassium into cells.
The incidence of transfusion-associated hyperkalemia in adults may be as high as 4%; it is lower in the pediatric population, the frequency of hyperkalemia is as low as about 1%.[35][36][37]
Hyperkalemia is seen in transfusions of blood products in the latter days of storage due to potassium leakage from cells.[4] Hyperkalemia may occur in irradiated red-cell preparations, which have a shorter shelf life of 28 days.
Result
may be low or high
serum bicarbonate
Test
Metabolic acidosis may be associated with large-volume blood transfusions due to contained citrate conversion into bicarbonate.
Result
may be low
serum calcium
Test
Hypocalcemia is uncommon. Associated with large-volume transfusions due to citrate contained in whole blood. Citrate complexes calcium, resulting in low ionized calcium.
Result
may be low
serum creatinine
Test
May indicate presence of renal failure.
Result
may be high
CBC
Test
Low hemoglobin may be seen with hemolytic anemia. Low platelets may suggest disseminated intravascular coagulation.
Eosinophilia and/or an acute decrease in neutrophil count may occur in transfusion-related acute lung injury (TRALI), but these associated findings do not necessarily rule in or disprove TRALI.
Result
may show reduction in hemoglobin or platelets
D-dimer
Test
May suggest presence of disseminated intravascular coagulation.
Result
may be elevated
PT and PTT
Test
Coagulation studies may be abnormal in disseminated intravascular coagulation.[1]
Result
may be abnormal
chest x-ray
Test
When transfusion-related acute lung injury (TRALI) is suspected, a chest x-ray should be obtained.[1] Evidence of bilateral patchy alveolar infiltrates supports the diagnosis. TRALI is clinically defined as the onset of acute lung injury in temporal relation to transfusion. Criteria for acute lung injury include acute onset of symptoms, absence of circulatory overload, bilateral pulmonary infiltrates on chest x-ray, and hypoxemia.
Result
may show bilateral patchy infiltrates in transfusion-related acute lung injury (TRALI)
arterial blood gas
Test
As demonstrated by PaO2/FIO2 <300 mmHg.
Result
may show hypoxemia in transfusion-related acute lung injury (TRALI)
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